New approaches for the effective recovery of fish proteins and their physicochemical characteristics

Abstract

Pacific whiting protein solubility was significantly affected as the pH shifted away from the isoelectric point (pH 5.5). The highest breaking force of gels was measured for fish proteins treated at pH 11, while high deformation values were obtained at pH 2 and 11. Sodium dodecylsulfatepolyacrylamide gel electrophoresis revealed that fish proteins were highly degraded by acid or alkali treatment. High activity of cathepsin B-like enzyme was detected from acid-aided fish proteins. Strong cathepsin L-like activity was found in fish proteins treated at pH 10.5, corresponding well to the lower breaking force and deformation. Disulfide bonds were thought to contribute to the high texture value of fish proteins treated at pH 11.KEY WORDS: acid-aided processing, alkali-aided processing, fish proteins, pH.

Producción y evaluación funcional de un concentrado proteico de calamar gigante (Dosidicus gigas) obtenido mediante disolución alcalina Production and functional evaluation of a protein concentrate from giant squid (Dosidicus gigas) obtained by alkaline dissolution

“…Dependiendo del pH estos aminoa´cidos pueden conferir a la proteı´na carga neta positiva o negativa, en donde la repulsio´n electrosta´tica es la responsable de la solubilidad. A pH s alcalinos, mayores a los valores de pḰ s de aminoa´cidos ba´sicos la proteı´na adquiere una carga neta negativa, producto de la ionizacio´n de aminoa´ci-dos a´cidos (ejerciendo carga negativa) y desprotonacio´n de aminoa´cidos alcalinos (grupo amino desprotonado, sin carga) (Kim, Park, & Choi, 2003). Nuestro resultado es ligeramente mayor al reportado por Corte´s-Ruiz et al (2008), quienes trabajando con la misma especie de calamar obtuvieron una solubilidad del 77,2 + 7,0% al solubilizar las proteı´nas del manto a un pH de 3,0.…”

Thermal gelation of myofibrillar proteins from aquatic organisms

“…Moreover, carp proteins showed a decrease in solubility, which was attributed to the formation of agglomerates. In addition, the formation of agglomerates has already been reported for other aquatic species when a pH shift is used (Kim et al, 2003;Tolano-Villaverde et al, 2013).…”

“…In addition, globular proteins exhibit a fine filament structure by forming filaments with small particles. Moreover, aggregate gels are formed when proteins are close to their isoelectric point, are more opaque, and have a lower WHC (Hermansson & Langton, 1994;Kim, Park, & Choi, 2003) due to protein aggregation, which favors a weaker protein-water interaction.…”

“…In these studies, it has been found that if the protein was treated with acid a higher hydrophobicity was detected compared to an alkaline-treated protein (Kim et al, 2003). Liu et al (2014) have studied the surimi silver carp and have reported that hydrophobic interactions contribute to gel stability because they significantly increase after denaturation occurs, which indicates that a large interaction between hydrophobic regions occurs after their unfolding.…”

“…Thus, the available SH groups are freed for S-S formation. Sulfhydryl groups (SH) are the most reactive functional groups in proteins (Fennema, 2000;Kim et al, 2003). Some authors have reported that SH and SS play an important role in the formation of rigid structures, such as gels, because they are involved in myosin aggregation mechanisms.…”